JP2011196620A - Ebullient cooling type heat exchanger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ebullient cooling type heat exchanger capable of being miniaturized while keeping its heat exchanging performance, and preventing burnout.SOLUTION: In a cooled-fluid flow channel 21, a flow channel cross-section of its upstream section 21a is smaller than that of the downstream section 21b, and in a refrigerant flow channel 24, a flow channel cross-section of its downstream section 24b is larger than that of the upstream section 24a.

Description

  The present invention relates to a boiling cooling heat exchanger.

  An EGR cooler (boiling cooling device) used for lowering the temperature of the EGR gas is disclosed in Patent Document 1, for example. The EGR cooler of Patent Document 1 includes a boiling evaporator (heat exchanger) that exchanges heat between the EGR gas recirculated from the exhaust system to the intake system and the refrigerant. This evaporator has a double pipe structure, and an EGR gas flow path (hereinafter referred to as “EGR gas flow path”) is formed inside the inner pipe, and between the inner pipe and the outer pipe. A refrigerant flow path (hereinafter referred to as “refrigerant flow path”) is formed by the space. In the evaporator, heat is exchanged between the EGR gas and the refrigerant through the inner pipe, and the refrigerant boils, and the EGR gas is cooled by the boiling vaporization latent heat at this time.

JP 2003-278607 A

  Incidentally, in the evaporator, the upstream side of the EGR gas flow path is hotter than the downstream side because EGR gas has just flowed into the EGR gas flow path. For this reason, the heat flux in the inner pipe is larger on the upstream side of the EGR gas flow path than on the downstream side. Here, in the heat exchanger, in order to avoid the occurrence of burnout, it is necessary to prevent the heat flux on the upstream side of the EGR gas flow path from exceeding the critical heat flux, and to the upstream side of the EGR gas flow path. It is necessary to secure a sufficient cross-sectional area of the corresponding refrigerant flow path.

  However, in the evaporator of Patent Document 1, the inner pipe and the outer pipe are provided so as to extend parallel to each other from the inlet toward the outlet, and the flow path cross-sectional area of the refrigerant flow path is from the inlet of the refrigerant flow path to the outlet. It is constant toward. As described above, the flow passage cross-sectional area of the refrigerant flow passage has a sufficient margin to avoid the occurrence of burnout, and therefore, at a position corresponding to the downstream side of the EGR gas flow passage where the heat flux is reduced. The critical heat flux is much larger than the heat flux in the inner pipe, and the heat exchange performance of the evaporator is more than necessary. As a result, the heat exchanger itself has become unnecessarily large.

  An object of the present invention is to provide a boil-cooled heat exchanger that can be downsized while maintaining heat exchange performance and can avoid the occurrence of burnout.

  In order to achieve the above object, the invention according to claim 1 is a boiling cooling system in which a cooled fluid channel through which a fluid to be cooled flows and a refrigerant channel through which a coolant for cooling the cooled fluid flows are partitioned by a partition wall. In the heat exchanger, the cross-sectional area of the refrigerant flow path corresponding to the upstream side of the flow direction of the cooled fluid in the flow path of the cooled fluid corresponds to the downstream side of the flow path of the cooled fluid The gist of the present invention is that there is a portion that is larger than the cross-sectional area of the refrigerant flow path.

  The upstream side of the cooled fluid channel is a partition located upstream of the cooled fluid channel because the cooled fluid is hot because the cooled fluid has just flowed into the cooled fluid channel. This heat flux tends to be larger than the heat flux of the partition located on the downstream side of the fluid flow path to be cooled. In addition, since the fluid to be cooled is gradually cooled by the refrigerant flowing through the refrigerant flow path, the fluid to be cooled is at a lower temperature on the downstream side of the fluid flow path than the upstream side, and the heat flow of the partition wall The bundle is smaller toward the downstream side of the fluid flow path to be cooled.

  In the present invention, the flow path cross-sectional area of the refrigerant flow path corresponding to the upstream side of the cooled fluid flow path is made larger than the flow path cross-sectional area of the refrigerant flow path corresponding to the downstream side of the cooled fluid flow path. The critical heat flux on the upstream side of the cooled fluid flow path can be increased. As a result, it is possible to avoid the occurrence of burnout in the partition wall in the refrigerant flow path corresponding to the upstream side of the fluid flow path to be cooled. In addition, the flow path cross-sectional area of the refrigerant flow path corresponding to the downstream side of the cooled fluid flow path is smaller than the flow path cross-sectional area of the refrigerant flow path corresponding to the upstream side of the cooled fluid flow path. The critical heat flux on the downstream side in the cooling fluid channel is small. Here, in the downstream portion of the fluid flow path to be cooled, the fluid to be cooled is cooled by the refrigerant and the heat flux of the partition wall is reduced, so that the heat flux of the partition wall does not exceed the critical heat flux, and the burnout Occurrence is avoided. As a result, the boiling cooling heat exchanger itself can be reduced in size while maintaining the heat exchange performance, and the occurrence of burnout can be avoided.

  According to a second aspect of the present invention, in the first aspect of the present invention, the cooled fluid channel has a small upstream channel cross-sectional area in the cooled fluid channel, and the cooled fluid channel. The gist of the present invention is that it gradually spreads from the upstream side to the downstream side of the fluid flow path to be cooled so that the cross-sectional area of the downstream side of the channel becomes larger.

  According to this, when the peripheral wall of the boiling cooling type heat exchanger is tapered so as to gradually widen from the upstream side to the downstream side of the refrigerant flow path, the flow passage sectional area on the downstream side in the refrigerant flow path is increased. Thus, the flow passage cross-sectional area on the downstream side in the refrigerant flow passage can be increased without increasing the size of the boiling cooling heat exchanger itself.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the flow direction of the cooled fluid that flows through the cooled fluid flow path and the flow direction of the refrigerant that flows through the refrigerant flow path are The gist is that they face each other.

  The temperature of the refrigerant flowing through the refrigerant flow path is lowest at the inlet and higher at the outlet side (downstream side). Further, the temperature of the cooled fluid flowing through the cooled fluid flow path is highest at the inlet and lower at the outlet side (downstream side). According to the present invention, since the fluid to be cooled whose temperature is low is cooled by the refrigerant having the lowest temperature, it is possible to make a temperature difference between the fluid to be cooled and the refrigerant. Therefore, for example, the heat exchange performance can be improved compared to the case where the cooled fluid having the highest temperature is cooled by the refrigerant having the lowest temperature, such as parallel flow.

  According to the present invention, it is possible to reduce the size while maintaining the heat exchange performance, and to avoid the occurrence of burnout.

The perspective view which shows the heat exchanger in embodiment. The longitudinal cross-sectional view of a heat exchanger. (A) is the AA line longitudinal cross-sectional view in FIG. 2, (b) is the BB line vertical cross-sectional view in FIG. The graph which shows the relationship between the flow direction of the to-be-cooled fluid flow path for a comparison, and the position in the flow direction of a refrigerant flow path, and a heat flux. The graph which shows the relationship in the distribution direction of a to-be-cooled fluid flow path, the position in the distribution direction of a refrigerant flow path, and a heat flux. The longitudinal cross-sectional view which shows the heat exchanger in another embodiment. (A) is the CC sectional view taken on the line in FIG. 6, (b) is the DD sectional view taken on the line in FIG. The perspective view which shows the heat exchanger in another embodiment.

  Hereinafter, the present invention is a boiling cooling type heat exchanger (hereinafter, simply referred to as “heat exchanger”) of an EGR gas boiling cooling device (EGR cooler) in an exhaust gas recirculation (EGR) of a vehicle. 1 to 5 will be described with reference to FIGS. The heat exchanger 11 of the exhaust gas recirculation device performs heat exchange between the EGR gas as the fluid to be cooled and the water (liquid refrigerant) as the refrigerant, and boiles part of the water to cool the EGR gas. In the following description, when referring to the “front-rear direction”, the direction indicated by the arrow Y1 in FIG. 1 is the “front-rear direction” unless otherwise specified.

  As shown in FIG. 1, a heat exchange section 13 is accommodated in a substantially cylindrical housing 12 that forms an outline of the heat exchanger 11. In the housing 12, a cooled fluid introduction unit 14 is provided on the front side (one side) of the heat exchange unit 13, and on the rear side (the other side) of the heat exchange unit 13, the cooled fluid discharge unit 15. Is provided.

  The front end (one end) surface of the housing 12 is connected to an introduction pipe 16 for introducing the EGR gas into the fluid to be cooled introduction portion 14, and the rear end (other end) surface of the housing 12 is connected to the EGR gas. Is connected to the cooling fluid discharge part 15. The heat exchanger 11 is used with the introduction pipe 16 connected to the EGR passage inlet side and the discharge pipe 17 connected to the EGR passage outlet side.

  Near the rear end (other end) of the peripheral wall of the housing 12, two refrigerant introduction pipes 22 for introducing water into the heat exchanging portion 13 in the housing 12 are connected, and two refrigerant introduction pipes 22 are connected. Are connected to opposite positions of the housing 12. In addition, two refrigerant discharge pipes 23 for discharging water from the heat exchange unit 13 are connected to the front end (one end) of the peripheral wall of the housing 12, and the two refrigerant discharge pipes 23 are connected to the housing 12. They are connected to positions facing each other. The refrigerant introduction pipe 22 is connected to one end of a water circulation line (not shown), and the refrigerant discharge pipe 23 is connected to the other end of the circulation line.

  The heat exchanging unit 13 includes a plurality (five in this embodiment) of pipes (pipes) 18, a front wall 13 a joined to the front (one) open end of the pipe 18, and a rear (other) open end. And a joined rear wall 13b. The pipe 18 is arranged such that the front opening is located on the cooled fluid introduction part 14 side and the rear opening is located on the cooled fluid discharge part 15 side.

  As shown in FIG. 2, an introduction hole 13c is formed in the front wall 13a at a site corresponding to the front opening of the pipe 18, and the inside of the pipe 18 and the fluid-to-be-cooled introduction part 14 are connected via the introduction hole 13c. Are communicating. The rear wall 13b is formed with a discharge hole 13d at a portion corresponding to the rear opening of the pipe 18, and the inside of the pipe 18 and the cooled fluid discharge portion 15 are communicated with each other through the discharge hole 13d. .

  The EGR gas that has flowed into the cooled fluid introducing portion 14 from the introduction pipe 16 flows into the pipe 18 through the introduction hole 13c in the front wall 13a, and is covered through the discharge hole 13d in the rear wall 13b. It flows out to the cooling fluid discharge part 15 and flows into the EGR passage outlet side via the discharge pipe 17. Therefore, as shown in FIG. 2, a cooled fluid flow path 21 through which the EGR gas flows is formed in the pipe 18.

  In the fluid flow path 21 to be cooled, the opening in front of the pipe 18 is used as an EGR gas inlet, and the inlet side of the pipe 18 is a flow path to be cooled in the flow direction of the EGR gas (the direction of the arrow X1 shown in FIG. 2). 21 upstream. Further, in the fluid flow path 21 to be cooled, the opening behind the pipe 18 is an outlet, and the outlet side of the pipe 18 is a downstream side of the fluid flow path 21 in the flow direction of the EGR gas. Here, the “upstream side of the fluid flow path 21 to be cooled” in the present embodiment refers to a region from the central portion in the flow direction in the fluid flow path 21 to be cooled to the inlet side. , “The upstream portion 21a of the fluid flow path 21 to be cooled”. In addition, the “downstream side of the fluid flow path 21 to be cooled” in the present embodiment refers to a region from the central portion in the flow direction in the fluid flow path 21 to be cooled to the outlet side. It is assumed that “the downstream part 21 b of the fluid flow path 21 to be cooled”.

  The pipe diameter (outer diameter) of the pipe 18 is formed in a tapered shape so as to gradually increase from the front wall 13a to the rear wall 13b, that is, from the upstream portion 21a to the downstream portion 21b of the fluid flow path 21 to be cooled. . As shown in FIGS. 3A and 3B, the pipe diameter R1 of the pipe 18 in the upstream portion 21a of the cooled fluid flow path 21 is equal to the pipe diameter R2 of the pipe 18 in the downstream portion 21b of the cooled fluid flow path 21. Is smaller than For this reason, the channel cross-sectional area of the cooled fluid channel 21 gradually increases from the upstream portion 21a toward the downstream portion 21b.

  In the heat exchange section 13, a refrigerant flow path 24 is defined on the outside of the pipe 18 in a space surrounded by the housing 12, the front wall 13 a and the rear wall 13 b. That is, the refrigerant flow path 24 is provided so as to surround the cooled fluid flow path 21, and the tube wall 19 of the pipe 18 forms a partition that partitions the cooled fluid flow path 21 and the refrigerant flow path 24. ing. Then, water is introduced into the refrigerant flow path 24 from the two refrigerant introduction pipes 22, and the water that has passed through the refrigerant flow path 24 flows out into the two refrigerant discharge pipes 23 and is returned to the circulation line. .

  In the refrigerant flow path 24, the refrigerant introduction pipe 22 side is the upstream side of the refrigerant flow path 24 in the water flow direction (the direction of the arrow X2 shown in FIG. 2). In the refrigerant flow path 24, the refrigerant discharge pipe 23 side is the downstream side of the refrigerant flow path 24 in the water flow direction. Here, the “upstream side of the refrigerant flow path 24” in the present embodiment refers to a region extending from the central portion in the flow direction of the refrigerant flow path 24 to the refrigerant introduction pipe 22 side. The upstream portion 24a "of the refrigerant flow path 24 is assumed. In addition, the “downstream side of the refrigerant flow path 24” in the present embodiment refers to a region extending from the central portion in the flow direction of the refrigerant flow path 24 to the refrigerant discharge pipe 23 side. The downstream portion 24b of the flow path 24 ”.

  The flow passage cross-sectional area of the refrigerant flow passage 24 gradually increases from the upstream portion 24a of the refrigerant flow passage 24 toward the downstream portion 24b. As a result, the flow path cross-sectional area in the downstream portion 24b of the refrigerant flow path 24 corresponding to the upstream portion 21a of the cooled fluid flow path 21 is upstream of the refrigerant flow path 24 corresponding to the downstream portion 21b of the cooled fluid flow path 21. It is larger than the cross-sectional area of the channel in the portion 24a. Moreover, the flow of EGR gas and water in the heat exchanger 11 in this embodiment is a counter flow in which the flow direction of the EGR gas and the flow direction of the water face each other.

  Here, in the graph of FIG. 4, the limit heat flux when the channel cross-sectional areas of the cooled fluid channel 21 and the refrigerant channel 24 are constant from the upstream portions 21 a and 24 a to the downstream portions 21 b and 24 b in the flow direction. (Solid line) and heat flux (dashed line) are shown. The graph of FIG. 4 shows the relationship between the flow direction of the fluid flow path 21 to be cooled and the position (horizontal axis) in the flow direction of the refrigerant flow path 24 and the heat flux (vertical axis).

  As shown in the graph of FIG. 4, the EGR gas has a high temperature because it has just flown into the cooled fluid flow path 21 in the upstream portion 21a of the cooled fluid flow path 21, and the water flows toward the downstream portion 21b. It is cooled by heat exchange with and becomes low temperature. For this reason, as shown by the broken line in FIG. 4, the heat flux of the tube wall 19 increases toward the upstream portion 21 a side of the cooled fluid channel 21 and decreases toward the downstream portion 21 b of the cooled fluid channel 21.

  On the other hand, water is low in temperature immediately after flowing into the refrigerant flow path 24 in the upstream portion 24a of the refrigerant flow path 24, and partly boils due to heat exchange with the EGR gas toward the downstream portion 24b. Water and bubbles are mixed. Then, the water moves in the refrigerant flow path 24 toward the outlet of the refrigerant flow path 24 while being mixed with the bubbles. Since the bubbles merge with each other and increase in number as they go to the downstream portion 24b of the refrigerant flow path 24, the critical heat flux is upstream of the refrigerant flow path 24 as shown by the solid line in FIG. It becomes small as it goes to the downstream part 24b from the part 24a.

  In the present embodiment, as shown in FIG. 2, the fluid flow path 21 to be cooled has a smaller cross-sectional area in the upstream portion 21 a where the heat flux of the tube wall 19 becomes larger, and the heat flux of the tube wall 19 becomes smaller. The pipe 18 is formed in a tapered shape so that the downstream cross section 21b becomes larger in the cross-sectional area of the flow path. Further, the cooled fluid channel 21 has a channel cross-sectional area that is larger in the downstream portion 21b corresponding to the upstream portion 24a of the refrigerant channel 24 where the critical heat flux is larger, and is downstream of the refrigerant channel 24 where the critical heat flux is smaller. The upstream section 21a corresponding to the section 24b has a smaller channel cross-sectional area.

Next, the effect | action in the heat exchanger 11 of the said structure is demonstrated using the graph of FIG.4 and FIG.5.
Now, when the vehicle is operated, EGR gas, which is a part of the exhaust gas of the internal combustion engine, flows into the EGR passage inlet side and is cooled through the introduction pipe 16, the cooled fluid introduction portion 14, and the introduction hole 13c. It is introduced into the fluid flow path 21. The EGR gas introduced into the cooled fluid channel 21 flows from the inlet of the cooled fluid channel 21 toward the outlet.

  On the other hand, water is forcibly circulated in the circulation line by driving a pump (not shown) disposed on the circulation line, and is introduced into the refrigerant flow path 24 through the refrigerant introduction pipe 22. . The water introduced into the refrigerant channel 24 flows from the inlet to the outlet of the refrigerant channel 24.

  In the heat exchanger 11, the heat of the EGR gas is transferred to water through the tube wall 19. Here, the fluid flow channel 21 to be cooled has a smaller channel cross-sectional area toward the upstream portion 21a, and the refrigerant channel 24 has a larger channel cross-sectional area toward the downstream portion 24b. As a result, the critical heat flux at the upstream portion 21a of the fluid flow path 21 is increased. For this reason, even in the upstream portion 21a of the cooled fluid flow path 21 having a large heat flux, the heat flux of the tube wall 19 is prevented from exceeding the critical heat flux.

  Here, the graph of FIG. 5 shows the relationship between the position (horizontal axis) in the flow direction of the fluid flow path 21 to be cooled and the flow direction of the refrigerant flow path 24 in the present embodiment, and the heat flux (vertical axis). In addition, the critical heat flux is indicated by a solid line, and the heat flux is indicated by a broken line.

  As shown in the graph of FIG. 5, the limit heat flux is larger in the downstream portion 24 b of the refrigerant flow path 24, and is larger than the heat flux of the tube wall 19 even in the upstream portion 21 a of the cooled fluid flow path 21. ing. As a result, the occurrence of burnout in the pipe wall 19 can be avoided. Further, in the upstream portion 24a of the refrigerant flow path 24, the critical heat flux is small because the flow path cross-sectional area is small, but in the downstream portion 21b of the cooled fluid flow path 21, the EGR gas is cooled, The heat flux of the tube wall 19 does not exceed the critical heat flux.

  When heat is exchanged between the water and the EGR gas via the tube wall 19, the water boils and becomes steam at the tube wall 19, and flows in the cooled fluid channel 21 using the boiling vaporization latent heat. Cool the EGR gas. And the water which cooled EGR gas is discharged | emitted to a circulation line via the refrigerant | coolant discharge piping 23, and the water discharged | emitted to the circulation line is condensed by the refrigerant | coolant condensing part not shown provided in the circulation line. Then, it is supplied to the heat exchanger 11 again. The cooled EGR gas flows from the outlet of the fluid flow path 21 to the EGR passage outlet side through the discharge pipe 17, and the EGR gas that flows into the EGR passage outlet side is an intake system of the internal combustion engine. To reflux.

In the above embodiment, the following effects can be obtained.
(1) The fluid flow channel 21 to be cooled has a smaller channel cross-sectional area at the upstream portion 21a and a larger channel cross-sectional area at the downstream portion 21b. Even in the upstream portion 21a of the cooled fluid passage 21 where the temperature of the EGR gas is high and the heat flux of the tube wall 19 is large, the heat flow of the tube wall 19 can be increased by increasing the cross-sectional area of the refrigerant passage 24. The bundle can be made smaller than the critical heat flux to avoid burnout. Further, the flow passage cross-sectional area of the refrigerant flow passage 24 is smaller toward the upstream portion 24a, and the critical heat flux is smaller. However, since the EGR gas is at a low temperature in the downstream portion 21b of the cooled fluid channel 21, it is not necessary to ensure a large channel cross-sectional area of the refrigerant channel 24. As a result, the heat exchanger 11 itself can be downsized while maintaining the heat exchange performance, and the occurrence of burnout can be avoided.

  (2) The pipe 18 is gradually widened from the upstream portion 21a to the downstream portion 21b of the fluid channel 21 to be cooled to have a tapered shape, thereby increasing the channel cross-sectional area of the downstream portion 24b in the refrigerant channel 24. The channel cross-sectional area of the upstream portion 24a in the refrigerant channel 24 is reduced. Therefore, for example, as shown in FIG. 6, the peripheral wall of the housing 12 is tapered so as to gradually expand from the upstream portion 24 a to the downstream portion 24 b of the refrigerant flow path 24, and the flow path of the downstream portion 24 b in the refrigerant flow path 24. The channel cross-sectional area of the downstream portion 24b in the refrigerant channel 24 can be increased without increasing the size of the heat exchanger 11 itself as in the case of increasing the cross-sectional area.

  (3) The flow direction of the EGR gas flowing through the cooled fluid flow path 21 and the flow direction of water flowing through the refrigerant flow path 24 are opposed to each other. The temperature of water flowing through the refrigerant flow path 24 is lowest at the inlet and higher at the outlet side (downstream side). Further, the temperature of the EGR gas flowing through the cooled fluid flow path 21 is highest at the inlet and lower at the outlet side (downstream side). Therefore, in this embodiment, since the EGR gas having a low temperature is cooled by the water having the lowest temperature, it is possible to make a temperature difference between the EGR gas and the water. Therefore, for example, the heat exchange performance can be improved as compared with the case where the EGR gas having the highest temperature is cooled by the water having the lowest temperature as in the parallel flow.

  (4) Since the fluid channel 21 to be cooled gradually increases from the upstream portion 21a toward the downstream portion 21b, the cross-sectional area of the refrigerant passage 24 increases from the upstream portion 24a toward the downstream portion 24b. Gradually grows. Therefore, the critical heat flux can be gradually reduced as it goes from the upstream portion 21a to the downstream portion 21b of the cooled fluid flow path 21, and gradually as it goes from the upstream portion 21a to the downstream portion 21b of the cooled fluid flow path 21. Thus, the difference between the heat flux of the tube wall 19 and the critical heat flux that become smaller can be made uniform.

  (5) Since the channel cross-sectional area is smaller in the upstream portion 21 a in the cooled fluid channel 21, when a plurality of cooled fluid channels 21 are arranged, the upstream portion 21 a of the cooled fluid channel 21 The space | interval of adjacent pipe | tubes 18 can be expanded in the downstream part 24b of the corresponding refrigerant flow path 24. FIG. Therefore, it is possible to prevent the heat flux from increasing between the adjacent tubes 18 and to avoid the occurrence of burnout.

In addition, you may change the said embodiment as follows.
In embodiment, although the pipe | tube 18 was made into the taper shape, it is not restricted to this. For example, as shown in FIG. 6, the pipe 18 is formed in a straight tube shape so that the cross-sectional area of the flow path is constant from the upstream portion 21 a to the downstream portion 21 b of the cooled fluid flow path 21, and the peripheral wall of the housing 12 is You may form in the taper shape which spreads gradually from the upstream part 24a of the refrigerant flow path 24 to the downstream part 24b. As shown in FIGS. 7A and 7B, the tube diameter (outer diameter) R3 of the housing 12 corresponding to the upstream portion 21a of the fluid flow path 21 is connected to the downstream portion 21b of the fluid flow path 21. The tube diameter (outer diameter) R4 of the corresponding housing 12 is larger. Therefore, the flow path cross-sectional area of the refrigerant flow path 24 is increased toward the downstream portion 24b. According to this, in the downstream portion 24b of the refrigerant flow path 24, the interval between the tube 18 and the inner surface of the housing 12 is widened, and it is possible to prevent the heat flux from increasing between the tube 18 and the inner surface of the housing 12. In addition, the occurrence of burnout can be avoided. Moreover, since the amount of heat transfer in the downstream portion 21b of the cooled fluid channel 21 increases by increasing the channel cross-sectional area of the downstream portion 21b in the cooled fluid channel 21, the temperature of the EGR gas is further reduced. be able to.

  In embodiment, although the pipe | tube 18 was made into the taper shape, it is not restricted to this. For example, as shown in FIG. 8, the pipe 18 branched into two from the introduction pipe 16 is formed into a spiral shape, and the spiral pitch in the pipe 18 is extended from the upstream portion 21a to the downstream portion 21b of the cooled fluid flow path 21. It may be narrowed gradually. According to this, the ratio which the pipe | tube 18 occupies in the downstream part 24b of the refrigerant | coolant flow path 24 can be made smaller than the ratio which the pipe | tube 18 in the upstream part 24a of the refrigerant | coolant flow path 24 shows. As a result, in the cross section along the front-rear direction (the direction of the arrow Y1 shown in FIG. 8), the flow passage cross-sectional area of the downstream portion 24b in the refrigerant flow passage 24 corresponding to the upstream portion 21a of the fluid flow passage 21 to be cooled is increased. Can do. Moreover, in the upstream part 21a of the fluid flow path 21 to be cooled, the pitch of the spirals in the pipes 18 is large, so that the interval between the pipes 18 is widened and the heat flux between the pipes 18 is prevented from increasing. And the occurrence of burnout can be avoided.

  In the embodiment, the heat exchanging portion 13 includes the pipe 18 formed in a tapered shape so as to gradually increase from the upstream portion 21a to the downstream portion 21b of the fluid flow path 21. Not exclusively. For example, the heat exchanging unit 13 includes a straight tubular small-diameter portion extending so that the cross-sectional area of the channel is constant from the upstream side to the downstream side of the fluid flow path 21 to be cooled, and a portion near the outlet that is larger than the small-diameter portion. You may provide the pipe | tube which consists of an enlarged diameter part to diameter. In this way, in the heat exchanging unit 13, the refrigerant cross-sectional area of the refrigerant flow path 24 corresponding to the upstream side of the cooled fluid flow path 21 is the refrigerant flow path 24 corresponding to the downstream side of the cooled fluid flow path 21. There may be a portion that is larger than the flow path cross-sectional area. According to this, the same effect as the embodiment can be obtained.

  ○ In the heat exchanger 11 of the embodiment, the flow direction of the EGR gas and the water is an opposing flow, but not limited to this, for example, the flow direction of the EGR gas and the water is parallel to the same direction. It may be a parallel flow. Also in the heat exchanger that is a parallel flow, the channel cross-sectional area of the upstream portion 21a in the cooled fluid channel 21 is small and the channel cross-sectional area of the downstream portion 21b in the cooled fluid channel 21 is large as in the embodiment. Thus, by forming the pipe 18 in a tapered shape from the upstream portion 21a to the downstream portion 21b of the fluid flow path 21 to be cooled, the same effect as in the embodiment can be obtained.

In the embodiment, five pipes 18 constituting the fluid flow path 21 to be cooled are provided, but the number is not limited to this, and may be 1 to 4 or 6 or more.
In the embodiment, fins may be provided in at least one of the cooled fluid channel 21 and the coolant channel 24.

  Although this invention was applied to the heat exchanger 11 comprised by the to-be-cooled fluid flow path 21 comprised with the pipe | tube 18, and the refrigerant | coolant flow path 24 surrounding the circumference | surroundings of the pipe | tube 18, it is not restricted to this. For example, a plurality of passage partition bodies composed of two flat partition walls closed on both sides with a pair of spacer bars, a front wall joined to one opening end of each passage partition body, and joined to the other opening end You may apply to a plate type heat exchanger provided with a rear wall.

  In the embodiment, the heat exchanger 11 is embodied in the heat exchanger 11 provided in the EGR gas boiling cooling device (EGR cooler), but is not limited thereto, for example, a cooling device for an in-vehicle device, a refrigerator, Further, the heat exchanger may be embodied in a freezer or the like.

In the embodiment, the fluid to be cooled is the EGR gas. However, the present invention is not limited to this, and the fluid to be cooled may be a gas other than the EGR gas or a high-temperature liquid.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.

  (A) The cooled fluid flow path is composed of at least one pipe, and the refrigerant flow path is provided so as to surround the periphery of the pipe of the cooled fluid flow path. The boiling-cooling heat exchanger according to any one of claims 1 to 3.

  (B) The technical idea characterized in that the pipe is formed in a spiral shape and the pitch of the spiral in the pipe gradually decreases from the upstream portion to the downstream portion of the fluid flow path to be cooled ( A boiling cooling heat exchanger as described in a).

  DESCRIPTION OF SYMBOLS 11 ... Heat exchanger, 19 ... Tube wall as a partition, 21 ... Cooling fluid flow path, 24 ... Refrigerant flow path.

Claims (3)

A boiling cooling type heat exchanger in which a cooled fluid flow path through which a fluid to be cooled flows and a refrigerant flow path through which a refrigerant for cooling the cooled fluid flows are partitioned by a partition wall,
The flow path cross-sectional area of the refrigerant flow path corresponding to the upstream side in the flow direction of the cooled fluid flow path in the cooled fluid flow path corresponds to the downstream side of the cooled fluid flow path. A boiling-cooling heat exchanger characterized in that there is a portion that is larger than the cross-sectional area.   The cooled fluid flow path is configured such that the upstream flow path sectional area of the cooled fluid flow path is small and the downstream flow path cross sectional area of the cooled fluid flow path is large. The boiling cooling heat exchanger according to claim 1, wherein the boiling cooling heat exchanger gradually spreads from the upstream side to the downstream side of the flow path.   The boiling cooling according to claim 1 or 2, wherein a flow direction of the fluid to be cooled flowing through the flow channel to be cooled and a flow direction of the refrigerant flowing through the refrigerant flow channel are opposed to each other. Type heat exchanger.

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